计算简单液体化学势的代数微扰理论

在温度、体积不变的条件下插入一个粒子导致系统自由能的增量就是系统的化学势,利用该思想计算化学势时,首先把构型积分中涉及插入粒子与其它粒子的相互作用部分作Mayer展开,把粒子插入前后构型积分的比化成密度的幂级数,再利用代数微扰理论给出了一个新的计算化学势的公式,系统的过剩化学势可以表示成密度的幂级数形式,相应的系数可从两体、三体、及多体相关函数求出.利用所得的化学势公式计算了硬球流体的化学势,取微扰级数的前三项所得的结果在中低密度(约化密度从0到0.7)时与标准值符合得非常好,对于高密度情况,需要考虑微扰级数的更高级次.

Algebraic Perturbation Theory for Calculating Chemical Potentials of Simple Liquid

The chemical potential of a system is the increment of free energy when insert a particle in the system which its temperature and volume are kept constant.This idea is used to derive the formula for calculating chemical potential of a simple liquid.The part in configuration integral involved in the interaction between insert particle and other particles of the system are expended in Mayer series firstly.Then the ratio of configuration integrals between after inserted and before is expanded in power series of density.Treating configuration integrals with above step,the formula of calculating chemical potentials of a liquid are obtained by algebraic perturbation method.The excess chemical potentials of the system can be expressed in power series of density.Pair,triplet,up to n-body distribution function,determines the coefficient of nth term in the series.The chemical potentials of hard-core fluid are calculated by the formula in this paper.When the series of chemical potential formula are cut off in the third term,the results are in good agreement with the results obtained from the Carnahan-starling equation of state in the range of reduced density from 0 to 0.7.